1. Field of the Invention
The present invention relates to an ADC, and more particularly, to a sampling frequency of the ADC.
2. Description of the Prior Art
For an ADC, a correct phase of a sampling frequency of the ADC is very important. Auto phase setting is implemented to automatically adjust phases of a sampling frequency of an ADC in an electronic device, such as a liquid crystal display (LCD).
FIG. 1 is a timing diagram of a conventional phase setting method 100. The conventional method 100 comprises three steps: a phase-setting step, which is implemented to receive an auto phase setting instruction during a zeroth frame F0, a phase-measuring/calculating step, which is implemented to sample the image frame according to a zeroth phase P0 of a sampling frequency and to calculate characteristic values of the image frame corresponding to the zeroth phase P0 based on a predetermined algorithm during a first frame F1, and a phase characteristics-reading step, which is implemented to read (output) the characteristic values of the image frame corresponding to the zeroth phase P0 during a second frame F2. In the steps described above, any time interval between any two consecutive frames, such as the zeroth frame F0 and the first frame F1, is equal in length to a time interval between any two consecutive vertical synchronization signals Vsync of the image frame.
The conventional method 100 does not stop executing the above three steps on the image frame until acquiring the characteristic values of all the phases of the sampling frequency. By the analysis of the characteristic values (for example, determining the largest and the smallest characteristic values), an optimum sampling point is obtained and the phase adjustment, to use the optimum sampling point as the sampling point of the ADC, in the sampling frequency is completed.
According to the above, if the sampling frequency in the exemplary LCD includes N phases, the conventional method 100 has to take as long as 3N times the length of one frame to acquire the characteristic values corresponding to the N phases.
In general, the sampling frequency includes 32 phases, and a user has to wait about three to four seconds to see the set image frame IF set by the conventional method 100 to be displayed again on the LCD.